1. Technical Field
The technical Field relates to stereoscopic image viewing eyewear that is worn on a viewer for viewing a stereoscopic image.
2. Related Art
In recent years, stereoscopic image display devices for stereoscopically displaying still images and moving images are rapidly spreading due to factors such that development of their manufacturing technique reduces their price, the liquid crystal display devices are thinned and are lightweight, and image quality heightening technique in a display function is developed. Such stereoscopic image display devices are being widely applied to monitors of personal computers and digital TVs or the like for receiving digital broadcasting waves and performing display.
Variety of display systems of the stereoscopic image display devices are present, and most of them utilize parallax between human's right and left eyes to allow viewers to recognize a stereoscopic effect of displayed images. A conventional stereoscopic image display system includes a stereoscopic image display device for displaying right and left images alternately, and stereoscopic image viewing eyewear for receiving a synchronizing signal generated from this display device, and opening and closing left and right shutters in synchronization with the synchronizing signal.
U.S. Pat. No. 5,293,227 discloses control to be performed when the stereoscopic image viewing eyewear cannot receive a synchronizing signal in such a stereoscopic image display system. Specifically, in the control method disclosed in U.S. Pat. No. 5,293,227, when the stereoscopic image viewing eyewear cannot receive a synchronizing signal, the left and right shutters are simultaneously controlled to open or close.
The stereoscopic image viewing eyewear disclosed in U.S. Pat. No. 5,293,227 include a phase-locked loop that synchronizes synchronizing signals received by an infrared receiver, a mode control logic, a voltage controller that is controlled by the mode control logic and controls a voltage, and a driver that is controlled by the mode control logic and drives a right-eye LCC and a left-eye LCC. In the control of the stereoscopic image viewing eyewear, synchronizing signals received by the receiver are synchronized in the phase locked loop VCO, and the driver is driven based on a control instruction of the mode control logic. The driver drives the right-eye LCC and the left-eye LCC. The mode control logic changes a voltage by means of control of the phase locked loop VCO and switching of power from a battery. As a result, the stereoscopic image viewing eyewear simultaneously open and close the left and right shutters to allow a user with the eyewear to view non-stereoscopic images.
Incidentally, in the stereoscopic image display system, it is known that a display range of an object to be suitably viewed by a viewer in stereoscopic vision (a range of a direction perpendicular to display screen) changes according to a distance between the stereoscopic image display device and the viewer (refer to Non-Patent Document “Stereoscopic displays and visual comfort: a review”, Marc Lambooij, et al., 10.1117/2. 1200703.0648, SPIE Newsroom). FIG. 8 is a diagram describing a relationship between the distance from the stereoscopic image display device to the viewer and the display range of an object to be suitably viewed by the viewer in the stereoscopic vision. As shown in FIG. 8, the longer the distance from the stereoscopic image display device to the viewer becomes, the wider the display range of the object to be suitably viewed by the viewer in the stereoscopic vision becomes.